Report: Nearly half the ocean's animals died out in single generation

Since 1970, marine animal populations have declined by almost 50 percent. Some commercial fish families, including tuna and mackerel, have lost 75 percent of their stock, the WWF's Living Blue Planet Report states.

"Often that word 'emergency' gets bandied about, but in this situation it really is an emergency," said one WWF official in Australia.

Over-exploitation is the greatest threat to ocean species, but the warming climate is also driving the fastest changes in the oceans in millions of years. Temperatures are higher than ever before, and acidification is a significant problem.

One WWF official told The Guardian "We were taught in the 1980s that the solution to pollution is dilution, but that suggests the oceans have an infinite capacity to absorb our pollution. That is not true, and we have reached the capacity now."

The study finds the combined factors can do trillions of dollars of damage to worldwide economies every year. Economies that depend on fishing and local marine habitats are especially at risk.

But according to WWF, it's not too late to reverse the damage and prevent further devastation. Later this month, nations will meet to discuss the 2030 Agenda for Sustainable Development. WWF says it's essential that governments use that meeting to address ocean policy while there's still time.